The photomechanical process includes a step of transforming a continuous-gradation original image into a halftone-dot image, to which have so far been applied a super-high-contrast image reproducing photographic technique that employs an infectious development.
The emulsion of a lith-type silver halide light-sensitive material for use in the infectious development is a high-silver-chloride-content (at least 50 mol %) silver chlorobromide emulsion comprising uniformly shaped silver halide grains having an average grain size of about 0.2 .mu.m with a narrow grain size distribution. The lith-type silver halide light-sensitive material, when processed in an alkaline hydroquinone developer solution having a low sulfite ion concentration, i.e., a lith-type developer solution, can provide an image having a high contrast, a high sharpness and a high resolution.
The lith-type developer solution, however, is unpreservable because it is subject to degradation by oxidation, so it is difficult to keep its developability constant when used continuously.
There is known a method capable of rapidly forming a high-contrast image without using such a lith-type developer solution; for example, a method in which a hydrazine derivative is incorporated into the silver halide photographic light-sensitive material as described in JP O.P.I. No. 106244/1981. According to this technique, contrasty images can be obtained even by using a well preservable developer solution for rapid processing.
For halftone-dot-quality improvement there is a technique to incorporate a redox compound into the light-sensitive material as disclosed in JP O.P.I. No. 285340/1990. For wider halftone gradation JP O.P.I. No. 174143/1991 discloses a light-sensitive material comprising a redox compound-containing layer and a hydrazine derivative-containing light-sensitive emulsion layer.
However, the use of such redox compounds has problems to cause the light-sensitive material's sensitivity and contrast to deteriorate with storage time and pepper fog, so-called black spots, to appear on the processed unexposed area of the light-sensitive material, so it is the status quo that any satisfactory characteristics have not yet been obtained to date.